In 1985, when Carl Sagan was writing the novel Contact, he needed to quickly transport his protagonist Dr. Ellie Arroway from Earth to the star Vega. He had her enter a black hole and exit light-years away, but he didn’t know if this made any sense. The Cornell University astrophysicist and television star consulted his friend Kip Thorne, a bla ...…

Even as machines known as “deep neural networks” have learned to converse, drive cars, beat video games and Go champions, dream, paint pictures and help make scientific discoveries, they have also confounded their human creators, who never expected so-called “deep-learning” algorithms to work so well. No underlying principle has guided the desi ...…

You probably can’t remember what it feels like to play Super Mario Bros. for the very first time, but try to picture it. An 8-bit game world blinks into being: baby blue sky, tessellated stone ground, and in between, a squat, red-suited man standing still — waiting. He’s facing rightward; you nudge him farther in that direction. A few more step ...…

In 2006, a hunter shot what he thought was a polar bear in the Northwest Territories of Canada. Closer examination, however, revealed brown patches on its white fur, uncharacteristically long claws and a slightly hunched back. The creature was in fact a hybrid, its mother a polar bear, its father a grizzly. Although this cross was known to be p ...…

In the 1950s, Philip Anderson, a physicist at Bell Laboratories, discovered a strange phenomenon. In some situations where it seems as though waves should advance freely, they just stop — like a tsunami halting in the middle of the ocean. Anderson won the 1977 Nobel Prize in physics for his discovery of what is now called Anderson localization, ...…

On Dec. 13, 1972, Apollo 17 astronaut Harrison Schmitt walked up to a boulder in the moon’s Sea of Serenity. “This boulder’s got its own little track, right up the hill,” he called to his commander, Eugene Cernan, pointing out the mark the boulder left when it rolled down a mountainside. Cernan bounded over to collect some samples. “Think how i ...…

In 1950, John Nash — the mathematician later featured in the book and film “A Beautiful Mind” — wrote a two-page paper that transformed the theory of economics. His crucial, yet utterly simple, idea was that any competitive game has a notion of equilibrium: a collection of strategies, one for each player, such that no player can win more by uni ...…

One of the oldest problems in geometry asks which shapes tile the plane, locking together with copies of themselves to cover a flat area in an endless pattern called a tessellation. M.C. Escher’s drawings of tessellating lizards and other creatures illustrate that an unlimited variety of shapes can do this. The inventorying reduces to a finite, ...…

Parasites are among nature’s most skillful manipulators — and one of their specialties is making hosts perform reckless acts of irrational self-harm. There’s Toxoplasma gondii, which drives mice to seek out cats eager to eat them, and the liver fluke Dicrocoelium dendriticum, which motivates ants to climb blades of grass, exposing them to cows ...…

For years, dark matter has been behaving badly. The term was first invoked nearly 80 years ago by the astronomer Fritz Zwicky, who realized that some unseen gravitational force was needed to stop individual galaxies from escaping giant galaxy clusters. Later, Vera Rubin and Kent Ford used unseen dark matter to explain why galaxies themselves do ...…

The three young friends who devised the “happy ending” problem would become some of the most influential mathematicians of the 20th century, but were never able to solve their own puzzle. Now it receives its first big breakthrough.

Recent tests show that quantum computers made by D-Wave systems should solve some problems faster than ordinary computers. Researchers have begun to map out exactly which queries might benefit from these quantum machines.

An experiment claims to have invalidated a decades-old criticism against pilot-wave theory, an alternative formulation of quantum mechanics that eliminates the most baffling features of the subatomic universe.

The search for exotic new physical phenomena is being led by huge experiments like the Large Hadron Collider. But at the other end of the spectrum lie tabletop experiments — small-scale probes of hidden dimensions, dark matter and dark energy.